WO2007093793A1

WO2007093793A1 - A method op detecting a parameter in an annulus of a borehole

Info

Publication number: WO2007093793A1
Application number: PCT/GB2007/000520
Authority: WO
Inventors: Leslie David Jarvie; Shaun Compton Ross; Clarke Tennant
Original assignee: Metrol Technology Limited
Priority date: 2006-02-15
Filing date: 2007-02-15
Publication date: 2007-08-23
Also published as: GB0602986D0

Abstract

A method of detecting at least one parameter in an annulus of a borehole, the method comprising: providing a parameter sensing device (61) in an annulus (C) of a borehole; with the sensing device, sensing a parameter within the annulus thus producing an electrical signal from the sensing device; providing a transducer (41) in the borehole which communicates with the sensing device, and with the transducer converting the electrical signal to a propagatable signal such as an acoustic signal; propagating the signal from the transducer within the annulus to a receiver (43) outwith the annulus; and recovering said signal.

Description

A METHOD OF DETECTING A PARAMETER IN AN ANNULUS OF A BOREHOLE

The present invention relates to a method of determining a parameter in an annulus of a borehole, particularly but not exclusively of a subsea well. The present invention particularly relates to the measurement of pressure or temperature therein.

A well completion in a borehole generally comprises an outer casing enclosing production tubing with an annulus therebetween. Often further, generally concentric, casing strings are provided within the outer casing which result in a number of different annuli being defined between the adjacent strings of casing.

Ideally, the pressure, temperature and other properties of each annulus is monitored during work on or production from the well. If the temperature and/or pressure exceeds a pre-determined safety level then work on or production from the well can be paused or manipulated to prevent a leak from the annuli which may cause uncontrolled release of hydrocarbons or well fluids into the environment.

The pressure and temperature monitoring of such annuli can be performed on surface wellhead systems by having a port provided between the annulus and the surface wellhead. A sensor on the wellhead could determine the pressure, or temperature, and relay this information back to a control centre by any conventional means.

However a disadvantage with such an arrangement is that the port weakens the integrity of the sealed annulus and so provides a weak point at which the pressure and any fluids therein may leak. This in itself can result in hydrocarbons or well fluid escaping from the well and polluting the environment. Therefore certain operators may be reluctant to monitor the temperature and pressure of the annulus for this reason. Indeed for subsea wells, wellhead systems typically do not provide porting on the annuli due to the potential additional leak paths and the mechanical complexities of doing so.

According to a first aspect of the present invention, there is provided a method of detecting at least one parameter in an annulus of a borehole, the method comprising: providing a parameter sensing device in an annulus of a borehole; with the sensing device, sensing a parameter within the annulus thus producing an electrical signal from the sensing device; providing a transducer in the borehole which communicates with the sensing device, and with the transducer converting the electrical signal to a propagatable signal; propagating the propagatable signal from the transducer to a receiver outwith said annulus; and, recovering said propagatable signal.

The propagatable signal may be one of an acoustic signal, an electromagnetic signal and an inductive signal.

Preferably the receiver is outwith the borehole.

Alternatively, the receiver is in the borehole and the signal is onwardly transmitted to outwith the borehole by any suitable means such as a cable provided through porting, acoustic transmission as described herein or any other means. This is particularly useful where the signal is propagated inductively from an annulus which may be particularly difficult to obtain measurements from, to the centre of the borehole or a different annulus, where the signal can be recovered by conventional means, or by using a method according to the present invention.

Preferably the method is a method of quantifying the parameter in the annulus.

Thus since the signal from within the borehole is converted by the transducer to a propagatable signal, there is less or no need for physical porting and so the monitoring of the annulus parameter according to the present invention does not add a weak point to that annulus.

The annulus is typically defined by two tubular strings, such as two casing strings.

The borehole may comprise a plurality of annuli. Often three to four annuli may be defined. In particular the borehole may comprise a first innermost annulus and a second outer annulus, and the sensing device may be provided in the second outer annulus. The outer annulus may be adjacent to the innermost annulus or may be spaced apart from the innermost annulus by further annuli. However, the innermost annulus is adjacent to the centre of the borehole - no further annuli are provided between the innermost annulus and the centre of the borehole.

Thus the present invention also provides a method for determining a parameter in an annulus which is not the innermost annulus. These annuli have been hitherto especially difficult to monitor, particularly for subsea wells.

The transducer and sensing device are preferably provided in a housing together. Thus they are preferably provided in the same annulus. However the transducer need not be in the same annulus as the sensing device. The transducer may be in a different annulus or within the centre of an innermost tubular.

Data relating to the parameter may also be stored locally in the borehole for transmission at a later time.

The transducer may communicate with the sensing device by a direct physical connection or alternatively they may couple inductively, acoustically or by other means. In any one embodiment both options may be provided for: the transducer may be provided in a housing with the sensing device, and the sensing device may be adapted to couple inductively with a second transducer in a different annulus or elsewhere in the borehole. This would allow the sensing device to be used even if one transducer fails.

Moreover the present invention also allows the signal to be transmitted to a different annulus or the centre of the borehole according to the invention and then onwardly transmitted acoustically, inductively or even by conventional means such as porting of an electrical cable, although the porting is less preferred. The porting in such an embodiment may be provided in an annulus or central bore which is less liable to leakage and so such embodiments provide an overall reduced risk of leakage since the porting is in an area of less risk compared to porting if used in the annulus housing the parameter sensing device. Moreover even if the porting is connected to a central bore or annulus which is more likely to leak, an advantage of certain embodiments of the invention is still present because less of the central bore/annuli have porting compared to that required in known systems because of the communication between ports and the central bore in accordance with the present invention - thus there is still a reduced likelihood for the overall system to leak compared with annulus having ports in two or more annuli/central bore.

Preferably the signal is propagated to a borehole attachment at the top of the borehole, such as a wellhead, tree, Blow-Out Preventor (BOP) or Temporary Abandonment Cap (TA Cap). The attachment is not necessarily locked onto the top of the borehole.

The signal may be converted back into an electrical signal typically at the borehole attachment. The information from the signal may be stored at the borehole attachment or may be transmitted onwards by a variety of means to a control centre, typically separate from the borehole. For onshore boreholes, this may be close by the borehole or remote from the borehole. For subsea boreholes, this may be a ship or oil rig for example. In one embodiment, sonar is used to onwardly transmit the data to the control centre. In another embodiment, a cable may be used to onwardly transmit the data to the control centre.

The parameter may be temperature and/or pressure and/or other parameters such as vibration.

Preferably the transducer in the annulus is proximate to the top of the borehole, typically the wellhead. Typically the transducer is within 300m, preferably 200m, more preferably 100m, even more preferably within 50m from the top of the borehole. For certain embodiments, the transducer is 10 - 20m from the top of the borehole, although for other embodiments the transducer may be any distance from the borehole.

Preferably the sensing device is proximate to the top of the borehole, typically the wellhead. Typically the sensing device is within 300m, preferably 200m, more preferably 10Om, even more preferably within 50m from the top of the borehole. For certain embodiments, the sensing device is 10 - 20m from the top of the borehole, although for other embodiments the sensing device may be any distance from the borehole.

Optionally repeating devices may be provided in the borehole - especially when the transducer is spaced from the top of the borehole. The repeaters typically receive, amplify and retransmit the signal from the transducer. The repeaters may be in the same or different annuli or in the centre of the borehole.

The transducer in the annulus may also be able to receive data. The data received may request data on the parameters to be sent outwith the borehole or may request data on any parameters previously stored locally within the borehole; or the data may be to update software settings within the transducer.

The data may be instructions to operate downhole devices. A means may therefore be provided to operate downhole devices such as valves, chemical release, guns, sleeves etcetera.

Thus the transducer may be bi-directional.

A plurality of transducers may be provided.

A plurality of sensing devices may be provided.

A well may have two, three or more annuli. A transducer as described herein along with a sensing device may be provided in more than one or each annulus. Typically the borehole is a well. The well may be a geothermal well, an injection well, such as a water injection well; an observation well or any other type of well.

Preferably the well is a production well, especially a hydrocarbon producing well.

Hydrocarbons may be recovered from the well at the same time as the detecting operation according to the invention is carried out. This is particularly useful because the hydrocarbons' temperature may vary over time and in extreme cases could cause the wells to collapse. The invention is particularly useful for use in subsea wells in deep water.

Preferably therefore the borehole is a permanent completion well. A permanent completion well is a well which is expected to produce fluids for a long period of time, for example more than one year. In contrast a temporary completion well typically lasts for up to six months.

However the present invention can also be applied whilst drilling or completing a well. The information used can also prevent a catastrophic failure of the well and provide data such as pressure, temperature and vibration during construction of the well which will aid future well design. For example, more heat dissipation of the produced fluid at the bottom of the well is sometimes preferred and embodiments of the present invention can monitor the effectiveness of various well designs at various spaced apart points in doing this, thus providing feedback to allow improved heat dissipation in the future. Thus the parameter may be detected at spaced apart locations in the same annulus. There may be two such parameter sensing devices, or a series of parameter sensing devices; preferably all spaced apart in the same annulus. The spaced apart locations of some of the parameter sensing devices are typically at least 20m away from each other, but this does not typically exclude embodiments which have further sensing devices at intermediate distances - for example if five sensing devices were provided at 5m spacings between successive sensing devices, then the technical advantage of having two sensing devices at least 20m from each other would still be provided and such an embodiment would be within the scope of the preferred embodiment having two sensing devices at least 20m from each other. Alternatively where only two and no more sensing devices spaced apart by 5m are provided, this is less preferred and outwith the scope of the preferred embodiment which has some sensing devices spaced apart by at least 20m, although still within the scope of the present invention. Preferably there are sensing devices 50m away from each other and may be more than 100m or even more than 200m away from each other for certain embodiments; again notwithstanding that further sensing devices may be provided between the sensing devices spaced apart by said distances.

A device such as a shear valve may be provided to release the pressure within the annulus if it exceeds a safe limit.

The method may be performed when a blow-out preventor is attached to the well. Thus the method may be performed during drilling of the well, well intervention, or during completion of the well.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which: Fig. 1 is a cross-sectional view of a subsea well and tree; Fig. 2. is a block diagram of a communications device; Fig. 3 is a block diagram of a receiving device; Fig. 4 is a cross-sectional view of a subsea tree and well using inductive communication devices in accordance with the present invention;

Fig. 5 is a cross-sectional view of a subsea well being drilled and monitored according to the present invention.

Referring to Fig. 1 there is shown a subsea tree 10 connected to a wellhead 14 of a completed subsea well 12; the well 12 comprising a series of concentric casing strings 21 , 22, 23 and tubing string 24. Annuli 31 , 32, 33 are defined between the tubular strings 21-24.

A first communication device 41 is provided in the annulus 31 between the outermost casing 21 and the adjacent casing 22. A second communications device 42 is provided in the annulus 32 between the casing strings 22 and 23. Each communication device 41 , 42 is connected to a combined temperature and pressure sensor 61 , 62 and a transducer 68, 69.

For certain embodiments, the transducer, communications devices and sensing devices can be separate or even provided in different annuli. When provided in different annuli, the devices can communicate inductively, acoustically or by other means. In particular, the sensing device and transducer may be provided in a single housing and connected to a separate communication device. A tubing hanger 52 and casing hangers 54, 56 are also provided to mount the tubular strings 22-24 as is conventional in the art. The casing string 21 is attached to the wellhead 14.

In the subsea tree 10 a receiver 43 is provided which can receive acoustic signals from the communication devices 41 , 42. In certain alternative embodiments a two-way communication device may be provided in annuli 31 -33 so that acoustic signals may be sent from the tree 10 to the annuli 31-33. These signals may be used to control downhole sleeves, chemical release devices, valves, or to retrieve historical data previously stored locally or for any other reason.

Cables 45 or other communication system (not shown) are also provided in the tree 10 to transmit data onwardly to a host facility.

The tree 10 also comprises valves 11. During intervention or during completion, a blow-out preventor (not shown) may be provided on the wellhead 14 in place of, or in addition to, the tree 11.

Thus in use the sensors measure the pressure and temperature in the annuli 31 , 32. This information is passed to the respective transducers 68, 69 which convert the information to acoustic energy. The information is then acoustically transmitted by the communication devices 41 , 42 to the receiver 43 in the tree 10 and then onwards to a host facility. Thus important information regarding the temperature and pressure of the annuli 31 , 32 may be provided.

Sensors and transmission devices may be provided in the other annuli in addition to or instead of the annuli 31 , 32. An advantage of embodiments of the present invention is that information may be provided regarding the temperature and pressure of the annuli, especially the outer annuli such as annuli 31 and 32 in addition to an innermost annulus, such as the annulus 33.

A particular advantage of embodiments of the invention is that no porting is necessary in order to provide the temperature or pressure information.

Embodiments of the invention may be used for leak monitoring and checking the integrity of the casing.

For certain embodiments, the communication devices, such as the communication devices 41 , 42, are bi-directional. They can receive requests for information on the pressure and temperature of the annuli including previously locally stored data. They can also be used to control downhole devices such as valves, chemical release devices, or sleeves.

The communication devices 41 , 42 can be of a known design. Referring to Fig. 2, the communication devices 41 , 42 each comprise a transmitter (not shown) powered by a battery (not shown), a transducer 68, 69 and a thermometer(not shown). The analogue pressure signal generated by the transducer 69 passes to an electronics module 70 in which it is digitised and serially encoded for transmission by a carrier frequency, suitably of 100Hz - 20 kHz. The resulting bursts of carrier are applied to a magnetostrictive transducer 71 comprising a coil formed around a core whose ends are rigidly fixed to the respective tubular 21 -24 at spaced apart locations. The digitally coded data is thus transformed into a longitudinal sonic wave in one of the tubular strings 21-24. The transmitter electronics module 70 in the present embodiment comprises a signal conditioning circuit 35, a digitising and encoding circuit 36, and a current driver 37. The details of these circuits do not form part of the present invention, and suitable circuitry will be readily apparent to those skilled in the art. The transducer 71 has a coil 39 connected to the current driver 37 and formed round a core schematically indicated at 38. Suitably, the core is a laminated rod of nickel of about 25 mm diameter. The length of the rod is chosen to suit the desired sonic frequency which is suitably in the range 100 Hz to 2OkHz, preferably 500Hz - 3 kHz.

Referring to Fig. 3, the receiver 43 comprises a filter 49 and a transducer 46 connected to an electronics module powered by a battery (not shown). The filter 49 is a mechanical band-pass filter tuned to the data carrier frequency, and serves to remove some of the acoustic noise in tubular 21- 24 which could otherwise swamp the electronics. The transducer 46 is a piezoelectric element. The filter 49 and transducer 46 are mechanically coupled in series, and the combination is rigidly mounted at its ends to one of the casing strings 21-24. Thus, the transducer 46 provides an electrical output representative of the sonic data signal. Electronic filters 47 and 48 are also provided and the signal may be retransmitted or colleted by any suitable means 44. The transmitter can also incorporate a receiver to permit bi-directional communications.

Fig. 4 shows an alternative embodiment of the present invention. Like parts have been referred to with the same numbers except preceded with a '1 ' and will not be described further. In place of the acoustic communication devices, inductive communications devices 146 - 148 are provided in each of the annuli 131 - 133. The devices are each attached to a sensing tool 161 - 163 and can transfer information received from the sensing tools 161 - 163 between each other - in particular the devices 146, 147 can send inductive signals to the communication device 148, which functions as a receiver. A cable 145 is provided through porting in the subsea tree and connected to cable 149 for onward communication from the innermost annulus 133 housing the communication device 148. It is noted that the porting communicates with the innermost annulus which is less likely to leak compared to the other annuli. Thus such an embodiment is an improvement over conventional systems where the porting must be provided in each annulus under analysis. The Fig. 4 embodiment could be modified to include one acoustic transmitting device for transmission between one annulus and outside the borehole in order to completely avoid the provision of porting; said acoustic device still communicating inductively with the other annuli.

Fig. 5 shows a further alternative embodiment of the present invention, like parts being preceded with a '2' and not further described. Fig. 5 shows an arrangement during drilling of the well. A blow out preventor 270 with ram blocks 271 is provided at the top of the well in place of the subsea tree and a wear bushing 282 in place of a tubing hanger. A riser 272 includes a drill string 81 for performing the drilling as is conventional. The invention operates in a similar manner as described above with respect to the Fig. 1 embodiment - the annuli are monitored for temperature and pressure by sensing devices 261 , 262 and the information is converted to acoustic signals which are sent outwith the borehole to a communication tool 243.

Modifications may be made within the scope of the invention. For example, the transmitter transducer may impart a torsional, rather than a longitudinal, sonic vibration to the tubular. Transducers of other than magnetostrictive type may be used, such as piezoelectric crystals or polymers.

Claims

1. A method of detecting at least one parameter in an annulus of a borehole, the method comprising: providing a parameter sensing device in an annulus of a borehole; with the sensing device, sensing a parameter within the annulus thus producing an electrical signal from the sensing device; providing a transducer in the borehole which communicates with the sensing device, and with the transducer converting the electrical signal to a propagatable signal; propagating the propagatable signal from the transducer to a receiver outwith said annulus; and, recovering said propagatable signal.

2. A method as claimed in claim 1 , wherein the propagatable signal is an acoustic signal.

3. A method as claimed in claim 1 , wherein the propagatable signal is an inductive signal.

4. A method as claimed in any preceding claim, wherein the receiver is outwith the borehole.

5. A method as claimed in any one of claims 1 to 3, wherein the receiver is in the borehole and the signal is onwardly transmitted to outwith the borehole.

6. A method as claimed in any preceding claim, wherein the method is a method of quantifying the parameter in the annulus.

7. A method as claimed in any preceding claim, wherein the borehole comprises a first innermost annulus and a second outer annulus, and the sensing device is provided in the second outer annulus.

8. A method as claimed in any preceding claim, wherein the borehole is a well, typically a subsea well.

9. A method as claimed in any preceding claim, wherein the borehole is a hydrocarbon production well.

10. A method as claimed in claim 9, wherein hydrocarbons are recovered from the well at the same time as detecting the parameter in said annulus.

11. A method as claimed in claim 1 - 9, wherein a portion of the borehole is being drilled or completed at the same time as detecting the parameter in the annulus.

12. A method as claimed in any preceding claim, wherein the parameter is detected at spaced apart locations in the same annulus.

13. A method as claimed in any preceding claim, wherein the parameter sensed is temperature

14. A method as claimed in any preceding claim, wherein the parameter sensed is pressure.

15. A method as claimed in any preceding claim, wherein, the data is communicated to a second annulus or to a central bore.

16. A method as claimed in any preceding claim, wherein the signal is propagated to a borehole attachment at the top of the borehole.

17. A method as claimed in claim 16, wherein the signal is converted back into an electrical signal at the borehole attachment.

18. A method as claimed in any preceding claim, wherein the well comprises a plurality of annuli and at least one said transducer is provided in each of at least two of said annuli.

19. A method as claimed in any preceding claim, wherein the transducer in the annulus is within 500m of the top of the borehole, such as the seabed.

20. A method as claimed in claim 19, wherein the transducer in the annulus is within 20m of the top of the borehole, such as the seabed.

21. A method as claimed in any preceding claim, wherein the sensing device in the annulus is within 500m of the top of the borehole, such as the seabed.

22. A method as claimed in claim 21 , wherein the sensing device in the annulus is within 20m of the top of the borehole, such as the seabed.

23. A method as claimed in any preceding claim, wherein the transducer in the annulus is adapted to receive data.

24. A method as claimed in claim 23, wherein the data received is used to request data from the transducer.

25. A method as claimed in claim 23, wherein the data received is used to control downhole devices.